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1da177e4 LT |
1 | /* |
2 | * mm/page-writeback.c. | |
3 | * | |
4 | * Copyright (C) 2002, Linus Torvalds. | |
5 | * | |
6 | * Contains functions related to writing back dirty pages at the | |
7 | * address_space level. | |
8 | * | |
9 | * 10Apr2002 akpm@zip.com.au | |
10 | * Initial version | |
11 | */ | |
12 | ||
13 | #include <linux/kernel.h> | |
14 | #include <linux/module.h> | |
15 | #include <linux/spinlock.h> | |
16 | #include <linux/fs.h> | |
17 | #include <linux/mm.h> | |
18 | #include <linux/swap.h> | |
19 | #include <linux/slab.h> | |
20 | #include <linux/pagemap.h> | |
21 | #include <linux/writeback.h> | |
22 | #include <linux/init.h> | |
23 | #include <linux/backing-dev.h> | |
24 | #include <linux/blkdev.h> | |
25 | #include <linux/mpage.h> | |
26 | #include <linux/percpu.h> | |
27 | #include <linux/notifier.h> | |
28 | #include <linux/smp.h> | |
29 | #include <linux/sysctl.h> | |
30 | #include <linux/cpu.h> | |
31 | #include <linux/syscalls.h> | |
32 | ||
33 | /* | |
34 | * The maximum number of pages to writeout in a single bdflush/kupdate | |
35 | * operation. We do this so we don't hold I_LOCK against an inode for | |
36 | * enormous amounts of time, which would block a userspace task which has | |
37 | * been forced to throttle against that inode. Also, the code reevaluates | |
38 | * the dirty each time it has written this many pages. | |
39 | */ | |
40 | #define MAX_WRITEBACK_PAGES 1024 | |
41 | ||
42 | /* | |
43 | * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited | |
44 | * will look to see if it needs to force writeback or throttling. | |
45 | */ | |
46 | static long ratelimit_pages = 32; | |
47 | ||
48 | static long total_pages; /* The total number of pages in the machine. */ | |
49 | static int dirty_exceeded; /* Dirty mem may be over limit */ | |
50 | ||
51 | /* | |
52 | * When balance_dirty_pages decides that the caller needs to perform some | |
53 | * non-background writeback, this is how many pages it will attempt to write. | |
54 | * It should be somewhat larger than RATELIMIT_PAGES to ensure that reasonably | |
55 | * large amounts of I/O are submitted. | |
56 | */ | |
57 | static inline long sync_writeback_pages(void) | |
58 | { | |
59 | return ratelimit_pages + ratelimit_pages / 2; | |
60 | } | |
61 | ||
62 | /* The following parameters are exported via /proc/sys/vm */ | |
63 | ||
64 | /* | |
65 | * Start background writeback (via pdflush) at this percentage | |
66 | */ | |
67 | int dirty_background_ratio = 10; | |
68 | ||
69 | /* | |
70 | * The generator of dirty data starts writeback at this percentage | |
71 | */ | |
72 | int vm_dirty_ratio = 40; | |
73 | ||
74 | /* | |
75 | * The interval between `kupdate'-style writebacks, in centiseconds | |
76 | * (hundredths of a second) | |
77 | */ | |
78 | int dirty_writeback_centisecs = 5 * 100; | |
79 | ||
80 | /* | |
81 | * The longest number of centiseconds for which data is allowed to remain dirty | |
82 | */ | |
83 | int dirty_expire_centisecs = 30 * 100; | |
84 | ||
85 | /* | |
86 | * Flag that makes the machine dump writes/reads and block dirtyings. | |
87 | */ | |
88 | int block_dump; | |
89 | ||
90 | /* | |
91 | * Flag that puts the machine in "laptop mode". | |
92 | */ | |
93 | int laptop_mode; | |
94 | ||
95 | EXPORT_SYMBOL(laptop_mode); | |
96 | ||
97 | /* End of sysctl-exported parameters */ | |
98 | ||
99 | ||
100 | static void background_writeout(unsigned long _min_pages); | |
101 | ||
102 | struct writeback_state | |
103 | { | |
104 | unsigned long nr_dirty; | |
105 | unsigned long nr_unstable; | |
106 | unsigned long nr_mapped; | |
107 | unsigned long nr_writeback; | |
108 | }; | |
109 | ||
110 | static void get_writeback_state(struct writeback_state *wbs) | |
111 | { | |
112 | wbs->nr_dirty = read_page_state(nr_dirty); | |
113 | wbs->nr_unstable = read_page_state(nr_unstable); | |
114 | wbs->nr_mapped = read_page_state(nr_mapped); | |
115 | wbs->nr_writeback = read_page_state(nr_writeback); | |
116 | } | |
117 | ||
118 | /* | |
119 | * Work out the current dirty-memory clamping and background writeout | |
120 | * thresholds. | |
121 | * | |
122 | * The main aim here is to lower them aggressively if there is a lot of mapped | |
123 | * memory around. To avoid stressing page reclaim with lots of unreclaimable | |
124 | * pages. It is better to clamp down on writers than to start swapping, and | |
125 | * performing lots of scanning. | |
126 | * | |
127 | * We only allow 1/2 of the currently-unmapped memory to be dirtied. | |
128 | * | |
129 | * We don't permit the clamping level to fall below 5% - that is getting rather | |
130 | * excessive. | |
131 | * | |
132 | * We make sure that the background writeout level is below the adjusted | |
133 | * clamping level. | |
134 | */ | |
135 | static void | |
136 | get_dirty_limits(struct writeback_state *wbs, long *pbackground, long *pdirty, | |
137 | struct address_space *mapping) | |
138 | { | |
139 | int background_ratio; /* Percentages */ | |
140 | int dirty_ratio; | |
141 | int unmapped_ratio; | |
142 | long background; | |
143 | long dirty; | |
144 | unsigned long available_memory = total_pages; | |
145 | struct task_struct *tsk; | |
146 | ||
147 | get_writeback_state(wbs); | |
148 | ||
149 | #ifdef CONFIG_HIGHMEM | |
150 | /* | |
151 | * If this mapping can only allocate from low memory, | |
152 | * we exclude high memory from our count. | |
153 | */ | |
154 | if (mapping && !(mapping_gfp_mask(mapping) & __GFP_HIGHMEM)) | |
155 | available_memory -= totalhigh_pages; | |
156 | #endif | |
157 | ||
158 | ||
159 | unmapped_ratio = 100 - (wbs->nr_mapped * 100) / total_pages; | |
160 | ||
161 | dirty_ratio = vm_dirty_ratio; | |
162 | if (dirty_ratio > unmapped_ratio / 2) | |
163 | dirty_ratio = unmapped_ratio / 2; | |
164 | ||
165 | if (dirty_ratio < 5) | |
166 | dirty_ratio = 5; | |
167 | ||
168 | background_ratio = dirty_background_ratio; | |
169 | if (background_ratio >= dirty_ratio) | |
170 | background_ratio = dirty_ratio / 2; | |
171 | ||
172 | background = (background_ratio * available_memory) / 100; | |
173 | dirty = (dirty_ratio * available_memory) / 100; | |
174 | tsk = current; | |
175 | if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) { | |
176 | background += background / 4; | |
177 | dirty += dirty / 4; | |
178 | } | |
179 | *pbackground = background; | |
180 | *pdirty = dirty; | |
181 | } | |
182 | ||
183 | /* | |
184 | * balance_dirty_pages() must be called by processes which are generating dirty | |
185 | * data. It looks at the number of dirty pages in the machine and will force | |
186 | * the caller to perform writeback if the system is over `vm_dirty_ratio'. | |
187 | * If we're over `background_thresh' then pdflush is woken to perform some | |
188 | * writeout. | |
189 | */ | |
190 | static void balance_dirty_pages(struct address_space *mapping) | |
191 | { | |
192 | struct writeback_state wbs; | |
193 | long nr_reclaimable; | |
194 | long background_thresh; | |
195 | long dirty_thresh; | |
196 | unsigned long pages_written = 0; | |
197 | unsigned long write_chunk = sync_writeback_pages(); | |
198 | ||
199 | struct backing_dev_info *bdi = mapping->backing_dev_info; | |
200 | ||
201 | for (;;) { | |
202 | struct writeback_control wbc = { | |
203 | .bdi = bdi, | |
204 | .sync_mode = WB_SYNC_NONE, | |
205 | .older_than_this = NULL, | |
206 | .nr_to_write = write_chunk, | |
207 | }; | |
208 | ||
209 | get_dirty_limits(&wbs, &background_thresh, | |
210 | &dirty_thresh, mapping); | |
211 | nr_reclaimable = wbs.nr_dirty + wbs.nr_unstable; | |
212 | if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh) | |
213 | break; | |
214 | ||
215 | dirty_exceeded = 1; | |
216 | ||
217 | /* Note: nr_reclaimable denotes nr_dirty + nr_unstable. | |
218 | * Unstable writes are a feature of certain networked | |
219 | * filesystems (i.e. NFS) in which data may have been | |
220 | * written to the server's write cache, but has not yet | |
221 | * been flushed to permanent storage. | |
222 | */ | |
223 | if (nr_reclaimable) { | |
224 | writeback_inodes(&wbc); | |
225 | get_dirty_limits(&wbs, &background_thresh, | |
226 | &dirty_thresh, mapping); | |
227 | nr_reclaimable = wbs.nr_dirty + wbs.nr_unstable; | |
228 | if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh) | |
229 | break; | |
230 | pages_written += write_chunk - wbc.nr_to_write; | |
231 | if (pages_written >= write_chunk) | |
232 | break; /* We've done our duty */ | |
233 | } | |
234 | blk_congestion_wait(WRITE, HZ/10); | |
235 | } | |
236 | ||
237 | if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh) | |
238 | dirty_exceeded = 0; | |
239 | ||
240 | if (writeback_in_progress(bdi)) | |
241 | return; /* pdflush is already working this queue */ | |
242 | ||
243 | /* | |
244 | * In laptop mode, we wait until hitting the higher threshold before | |
245 | * starting background writeout, and then write out all the way down | |
246 | * to the lower threshold. So slow writers cause minimal disk activity. | |
247 | * | |
248 | * In normal mode, we start background writeout at the lower | |
249 | * background_thresh, to keep the amount of dirty memory low. | |
250 | */ | |
251 | if ((laptop_mode && pages_written) || | |
252 | (!laptop_mode && (nr_reclaimable > background_thresh))) | |
253 | pdflush_operation(background_writeout, 0); | |
254 | } | |
255 | ||
256 | /** | |
257 | * balance_dirty_pages_ratelimited - balance dirty memory state | |
67be2dd1 | 258 | * @mapping: address_space which was dirtied |
1da177e4 LT |
259 | * |
260 | * Processes which are dirtying memory should call in here once for each page | |
261 | * which was newly dirtied. The function will periodically check the system's | |
262 | * dirty state and will initiate writeback if needed. | |
263 | * | |
264 | * On really big machines, get_writeback_state is expensive, so try to avoid | |
265 | * calling it too often (ratelimiting). But once we're over the dirty memory | |
266 | * limit we decrease the ratelimiting by a lot, to prevent individual processes | |
267 | * from overshooting the limit by (ratelimit_pages) each. | |
268 | */ | |
269 | void balance_dirty_pages_ratelimited(struct address_space *mapping) | |
270 | { | |
271 | static DEFINE_PER_CPU(int, ratelimits) = 0; | |
272 | long ratelimit; | |
273 | ||
274 | ratelimit = ratelimit_pages; | |
275 | if (dirty_exceeded) | |
276 | ratelimit = 8; | |
277 | ||
278 | /* | |
279 | * Check the rate limiting. Also, we do not want to throttle real-time | |
280 | * tasks in balance_dirty_pages(). Period. | |
281 | */ | |
282 | if (get_cpu_var(ratelimits)++ >= ratelimit) { | |
283 | __get_cpu_var(ratelimits) = 0; | |
284 | put_cpu_var(ratelimits); | |
285 | balance_dirty_pages(mapping); | |
286 | return; | |
287 | } | |
288 | put_cpu_var(ratelimits); | |
289 | } | |
290 | EXPORT_SYMBOL(balance_dirty_pages_ratelimited); | |
291 | ||
292 | void throttle_vm_writeout(void) | |
293 | { | |
294 | struct writeback_state wbs; | |
295 | long background_thresh; | |
296 | long dirty_thresh; | |
297 | ||
298 | for ( ; ; ) { | |
299 | get_dirty_limits(&wbs, &background_thresh, &dirty_thresh, NULL); | |
300 | ||
301 | /* | |
302 | * Boost the allowable dirty threshold a bit for page | |
303 | * allocators so they don't get DoS'ed by heavy writers | |
304 | */ | |
305 | dirty_thresh += dirty_thresh / 10; /* wheeee... */ | |
306 | ||
307 | if (wbs.nr_unstable + wbs.nr_writeback <= dirty_thresh) | |
308 | break; | |
309 | blk_congestion_wait(WRITE, HZ/10); | |
310 | } | |
311 | } | |
312 | ||
313 | ||
314 | /* | |
315 | * writeback at least _min_pages, and keep writing until the amount of dirty | |
316 | * memory is less than the background threshold, or until we're all clean. | |
317 | */ | |
318 | static void background_writeout(unsigned long _min_pages) | |
319 | { | |
320 | long min_pages = _min_pages; | |
321 | struct writeback_control wbc = { | |
322 | .bdi = NULL, | |
323 | .sync_mode = WB_SYNC_NONE, | |
324 | .older_than_this = NULL, | |
325 | .nr_to_write = 0, | |
326 | .nonblocking = 1, | |
327 | }; | |
328 | ||
329 | for ( ; ; ) { | |
330 | struct writeback_state wbs; | |
331 | long background_thresh; | |
332 | long dirty_thresh; | |
333 | ||
334 | get_dirty_limits(&wbs, &background_thresh, &dirty_thresh, NULL); | |
335 | if (wbs.nr_dirty + wbs.nr_unstable < background_thresh | |
336 | && min_pages <= 0) | |
337 | break; | |
338 | wbc.encountered_congestion = 0; | |
339 | wbc.nr_to_write = MAX_WRITEBACK_PAGES; | |
340 | wbc.pages_skipped = 0; | |
341 | writeback_inodes(&wbc); | |
342 | min_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write; | |
343 | if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) { | |
344 | /* Wrote less than expected */ | |
345 | blk_congestion_wait(WRITE, HZ/10); | |
346 | if (!wbc.encountered_congestion) | |
347 | break; | |
348 | } | |
349 | } | |
350 | } | |
351 | ||
352 | /* | |
353 | * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back | |
354 | * the whole world. Returns 0 if a pdflush thread was dispatched. Returns | |
355 | * -1 if all pdflush threads were busy. | |
356 | */ | |
687a21ce | 357 | int wakeup_pdflush(long nr_pages) |
1da177e4 LT |
358 | { |
359 | if (nr_pages == 0) { | |
360 | struct writeback_state wbs; | |
361 | ||
362 | get_writeback_state(&wbs); | |
363 | nr_pages = wbs.nr_dirty + wbs.nr_unstable; | |
364 | } | |
365 | return pdflush_operation(background_writeout, nr_pages); | |
366 | } | |
367 | ||
368 | static void wb_timer_fn(unsigned long unused); | |
369 | static void laptop_timer_fn(unsigned long unused); | |
370 | ||
371 | static struct timer_list wb_timer = | |
372 | TIMER_INITIALIZER(wb_timer_fn, 0, 0); | |
373 | static struct timer_list laptop_mode_wb_timer = | |
374 | TIMER_INITIALIZER(laptop_timer_fn, 0, 0); | |
375 | ||
376 | /* | |
377 | * Periodic writeback of "old" data. | |
378 | * | |
379 | * Define "old": the first time one of an inode's pages is dirtied, we mark the | |
380 | * dirtying-time in the inode's address_space. So this periodic writeback code | |
381 | * just walks the superblock inode list, writing back any inodes which are | |
382 | * older than a specific point in time. | |
383 | * | |
384 | * Try to run once per dirty_writeback_centisecs. But if a writeback event | |
385 | * takes longer than a dirty_writeback_centisecs interval, then leave a | |
386 | * one-second gap. | |
387 | * | |
388 | * older_than_this takes precedence over nr_to_write. So we'll only write back | |
389 | * all dirty pages if they are all attached to "old" mappings. | |
390 | */ | |
391 | static void wb_kupdate(unsigned long arg) | |
392 | { | |
393 | unsigned long oldest_jif; | |
394 | unsigned long start_jif; | |
395 | unsigned long next_jif; | |
396 | long nr_to_write; | |
397 | struct writeback_state wbs; | |
398 | struct writeback_control wbc = { | |
399 | .bdi = NULL, | |
400 | .sync_mode = WB_SYNC_NONE, | |
401 | .older_than_this = &oldest_jif, | |
402 | .nr_to_write = 0, | |
403 | .nonblocking = 1, | |
404 | .for_kupdate = 1, | |
405 | }; | |
406 | ||
407 | sync_supers(); | |
408 | ||
409 | get_writeback_state(&wbs); | |
410 | oldest_jif = jiffies - (dirty_expire_centisecs * HZ) / 100; | |
411 | start_jif = jiffies; | |
412 | next_jif = start_jif + (dirty_writeback_centisecs * HZ) / 100; | |
413 | nr_to_write = wbs.nr_dirty + wbs.nr_unstable + | |
414 | (inodes_stat.nr_inodes - inodes_stat.nr_unused); | |
415 | while (nr_to_write > 0) { | |
416 | wbc.encountered_congestion = 0; | |
417 | wbc.nr_to_write = MAX_WRITEBACK_PAGES; | |
418 | writeback_inodes(&wbc); | |
419 | if (wbc.nr_to_write > 0) { | |
420 | if (wbc.encountered_congestion) | |
421 | blk_congestion_wait(WRITE, HZ/10); | |
422 | else | |
423 | break; /* All the old data is written */ | |
424 | } | |
425 | nr_to_write -= MAX_WRITEBACK_PAGES - wbc.nr_to_write; | |
426 | } | |
427 | if (time_before(next_jif, jiffies + HZ)) | |
428 | next_jif = jiffies + HZ; | |
429 | if (dirty_writeback_centisecs) | |
430 | mod_timer(&wb_timer, next_jif); | |
431 | } | |
432 | ||
433 | /* | |
434 | * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs | |
435 | */ | |
436 | int dirty_writeback_centisecs_handler(ctl_table *table, int write, | |
437 | struct file *file, void __user *buffer, size_t *length, loff_t *ppos) | |
438 | { | |
439 | proc_dointvec(table, write, file, buffer, length, ppos); | |
440 | if (dirty_writeback_centisecs) { | |
441 | mod_timer(&wb_timer, | |
442 | jiffies + (dirty_writeback_centisecs * HZ) / 100); | |
443 | } else { | |
444 | del_timer(&wb_timer); | |
445 | } | |
446 | return 0; | |
447 | } | |
448 | ||
449 | static void wb_timer_fn(unsigned long unused) | |
450 | { | |
451 | if (pdflush_operation(wb_kupdate, 0) < 0) | |
452 | mod_timer(&wb_timer, jiffies + HZ); /* delay 1 second */ | |
453 | } | |
454 | ||
455 | static void laptop_flush(unsigned long unused) | |
456 | { | |
457 | sys_sync(); | |
458 | } | |
459 | ||
460 | static void laptop_timer_fn(unsigned long unused) | |
461 | { | |
462 | pdflush_operation(laptop_flush, 0); | |
463 | } | |
464 | ||
465 | /* | |
466 | * We've spun up the disk and we're in laptop mode: schedule writeback | |
467 | * of all dirty data a few seconds from now. If the flush is already scheduled | |
468 | * then push it back - the user is still using the disk. | |
469 | */ | |
470 | void laptop_io_completion(void) | |
471 | { | |
472 | mod_timer(&laptop_mode_wb_timer, jiffies + laptop_mode * HZ); | |
473 | } | |
474 | ||
475 | /* | |
476 | * We're in laptop mode and we've just synced. The sync's writes will have | |
477 | * caused another writeback to be scheduled by laptop_io_completion. | |
478 | * Nothing needs to be written back anymore, so we unschedule the writeback. | |
479 | */ | |
480 | void laptop_sync_completion(void) | |
481 | { | |
482 | del_timer(&laptop_mode_wb_timer); | |
483 | } | |
484 | ||
485 | /* | |
486 | * If ratelimit_pages is too high then we can get into dirty-data overload | |
487 | * if a large number of processes all perform writes at the same time. | |
488 | * If it is too low then SMP machines will call the (expensive) | |
489 | * get_writeback_state too often. | |
490 | * | |
491 | * Here we set ratelimit_pages to a level which ensures that when all CPUs are | |
492 | * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory | |
493 | * thresholds before writeback cuts in. | |
494 | * | |
495 | * But the limit should not be set too high. Because it also controls the | |
496 | * amount of memory which the balance_dirty_pages() caller has to write back. | |
497 | * If this is too large then the caller will block on the IO queue all the | |
498 | * time. So limit it to four megabytes - the balance_dirty_pages() caller | |
499 | * will write six megabyte chunks, max. | |
500 | */ | |
501 | ||
502 | static void set_ratelimit(void) | |
503 | { | |
504 | ratelimit_pages = total_pages / (num_online_cpus() * 32); | |
505 | if (ratelimit_pages < 16) | |
506 | ratelimit_pages = 16; | |
507 | if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024) | |
508 | ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE; | |
509 | } | |
510 | ||
511 | static int | |
512 | ratelimit_handler(struct notifier_block *self, unsigned long u, void *v) | |
513 | { | |
514 | set_ratelimit(); | |
515 | return 0; | |
516 | } | |
517 | ||
518 | static struct notifier_block ratelimit_nb = { | |
519 | .notifier_call = ratelimit_handler, | |
520 | .next = NULL, | |
521 | }; | |
522 | ||
523 | /* | |
524 | * If the machine has a large highmem:lowmem ratio then scale back the default | |
525 | * dirty memory thresholds: allowing too much dirty highmem pins an excessive | |
526 | * number of buffer_heads. | |
527 | */ | |
528 | void __init page_writeback_init(void) | |
529 | { | |
530 | long buffer_pages = nr_free_buffer_pages(); | |
531 | long correction; | |
532 | ||
533 | total_pages = nr_free_pagecache_pages(); | |
534 | ||
535 | correction = (100 * 4 * buffer_pages) / total_pages; | |
536 | ||
537 | if (correction < 100) { | |
538 | dirty_background_ratio *= correction; | |
539 | dirty_background_ratio /= 100; | |
540 | vm_dirty_ratio *= correction; | |
541 | vm_dirty_ratio /= 100; | |
542 | ||
543 | if (dirty_background_ratio <= 0) | |
544 | dirty_background_ratio = 1; | |
545 | if (vm_dirty_ratio <= 0) | |
546 | vm_dirty_ratio = 1; | |
547 | } | |
548 | mod_timer(&wb_timer, jiffies + (dirty_writeback_centisecs * HZ) / 100); | |
549 | set_ratelimit(); | |
550 | register_cpu_notifier(&ratelimit_nb); | |
551 | } | |
552 | ||
553 | int do_writepages(struct address_space *mapping, struct writeback_control *wbc) | |
554 | { | |
555 | if (wbc->nr_to_write <= 0) | |
556 | return 0; | |
557 | if (mapping->a_ops->writepages) | |
558 | return mapping->a_ops->writepages(mapping, wbc); | |
559 | return generic_writepages(mapping, wbc); | |
560 | } | |
561 | ||
562 | /** | |
563 | * write_one_page - write out a single page and optionally wait on I/O | |
564 | * | |
67be2dd1 MW |
565 | * @page: the page to write |
566 | * @wait: if true, wait on writeout | |
1da177e4 LT |
567 | * |
568 | * The page must be locked by the caller and will be unlocked upon return. | |
569 | * | |
570 | * write_one_page() returns a negative error code if I/O failed. | |
571 | */ | |
572 | int write_one_page(struct page *page, int wait) | |
573 | { | |
574 | struct address_space *mapping = page->mapping; | |
575 | int ret = 0; | |
576 | struct writeback_control wbc = { | |
577 | .sync_mode = WB_SYNC_ALL, | |
578 | .nr_to_write = 1, | |
579 | }; | |
580 | ||
581 | BUG_ON(!PageLocked(page)); | |
582 | ||
583 | if (wait) | |
584 | wait_on_page_writeback(page); | |
585 | ||
586 | if (clear_page_dirty_for_io(page)) { | |
587 | page_cache_get(page); | |
588 | ret = mapping->a_ops->writepage(page, &wbc); | |
589 | if (ret == 0 && wait) { | |
590 | wait_on_page_writeback(page); | |
591 | if (PageError(page)) | |
592 | ret = -EIO; | |
593 | } | |
594 | page_cache_release(page); | |
595 | } else { | |
596 | unlock_page(page); | |
597 | } | |
598 | return ret; | |
599 | } | |
600 | EXPORT_SYMBOL(write_one_page); | |
601 | ||
602 | /* | |
603 | * For address_spaces which do not use buffers. Just tag the page as dirty in | |
604 | * its radix tree. | |
605 | * | |
606 | * This is also used when a single buffer is being dirtied: we want to set the | |
607 | * page dirty in that case, but not all the buffers. This is a "bottom-up" | |
608 | * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying. | |
609 | * | |
610 | * Most callers have locked the page, which pins the address_space in memory. | |
611 | * But zap_pte_range() does not lock the page, however in that case the | |
612 | * mapping is pinned by the vma's ->vm_file reference. | |
613 | * | |
614 | * We take care to handle the case where the page was truncated from the | |
615 | * mapping by re-checking page_mapping() insode tree_lock. | |
616 | */ | |
617 | int __set_page_dirty_nobuffers(struct page *page) | |
618 | { | |
619 | int ret = 0; | |
620 | ||
621 | if (!TestSetPageDirty(page)) { | |
622 | struct address_space *mapping = page_mapping(page); | |
623 | struct address_space *mapping2; | |
624 | ||
625 | if (mapping) { | |
626 | write_lock_irq(&mapping->tree_lock); | |
627 | mapping2 = page_mapping(page); | |
628 | if (mapping2) { /* Race with truncate? */ | |
629 | BUG_ON(mapping2 != mapping); | |
630 | if (mapping_cap_account_dirty(mapping)) | |
631 | inc_page_state(nr_dirty); | |
632 | radix_tree_tag_set(&mapping->page_tree, | |
633 | page_index(page), PAGECACHE_TAG_DIRTY); | |
634 | } | |
635 | write_unlock_irq(&mapping->tree_lock); | |
636 | if (mapping->host) { | |
637 | /* !PageAnon && !swapper_space */ | |
638 | __mark_inode_dirty(mapping->host, | |
639 | I_DIRTY_PAGES); | |
640 | } | |
641 | } | |
642 | } | |
643 | return ret; | |
644 | } | |
645 | EXPORT_SYMBOL(__set_page_dirty_nobuffers); | |
646 | ||
647 | /* | |
648 | * When a writepage implementation decides that it doesn't want to write this | |
649 | * page for some reason, it should redirty the locked page via | |
650 | * redirty_page_for_writepage() and it should then unlock the page and return 0 | |
651 | */ | |
652 | int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page) | |
653 | { | |
654 | wbc->pages_skipped++; | |
655 | return __set_page_dirty_nobuffers(page); | |
656 | } | |
657 | EXPORT_SYMBOL(redirty_page_for_writepage); | |
658 | ||
659 | /* | |
660 | * If the mapping doesn't provide a set_page_dirty a_op, then | |
661 | * just fall through and assume that it wants buffer_heads. | |
662 | */ | |
663 | int fastcall set_page_dirty(struct page *page) | |
664 | { | |
665 | struct address_space *mapping = page_mapping(page); | |
666 | ||
667 | if (likely(mapping)) { | |
668 | int (*spd)(struct page *) = mapping->a_ops->set_page_dirty; | |
669 | if (spd) | |
670 | return (*spd)(page); | |
671 | return __set_page_dirty_buffers(page); | |
672 | } | |
673 | if (!PageDirty(page)) | |
674 | SetPageDirty(page); | |
675 | return 0; | |
676 | } | |
677 | EXPORT_SYMBOL(set_page_dirty); | |
678 | ||
679 | /* | |
680 | * set_page_dirty() is racy if the caller has no reference against | |
681 | * page->mapping->host, and if the page is unlocked. This is because another | |
682 | * CPU could truncate the page off the mapping and then free the mapping. | |
683 | * | |
684 | * Usually, the page _is_ locked, or the caller is a user-space process which | |
685 | * holds a reference on the inode by having an open file. | |
686 | * | |
687 | * In other cases, the page should be locked before running set_page_dirty(). | |
688 | */ | |
689 | int set_page_dirty_lock(struct page *page) | |
690 | { | |
691 | int ret; | |
692 | ||
693 | lock_page(page); | |
694 | ret = set_page_dirty(page); | |
695 | unlock_page(page); | |
696 | return ret; | |
697 | } | |
698 | EXPORT_SYMBOL(set_page_dirty_lock); | |
699 | ||
700 | /* | |
701 | * Clear a page's dirty flag, while caring for dirty memory accounting. | |
702 | * Returns true if the page was previously dirty. | |
703 | */ | |
704 | int test_clear_page_dirty(struct page *page) | |
705 | { | |
706 | struct address_space *mapping = page_mapping(page); | |
707 | unsigned long flags; | |
708 | ||
709 | if (mapping) { | |
710 | write_lock_irqsave(&mapping->tree_lock, flags); | |
711 | if (TestClearPageDirty(page)) { | |
712 | radix_tree_tag_clear(&mapping->page_tree, | |
713 | page_index(page), | |
714 | PAGECACHE_TAG_DIRTY); | |
715 | write_unlock_irqrestore(&mapping->tree_lock, flags); | |
716 | if (mapping_cap_account_dirty(mapping)) | |
717 | dec_page_state(nr_dirty); | |
718 | return 1; | |
719 | } | |
720 | write_unlock_irqrestore(&mapping->tree_lock, flags); | |
721 | return 0; | |
722 | } | |
723 | return TestClearPageDirty(page); | |
724 | } | |
725 | EXPORT_SYMBOL(test_clear_page_dirty); | |
726 | ||
727 | /* | |
728 | * Clear a page's dirty flag, while caring for dirty memory accounting. | |
729 | * Returns true if the page was previously dirty. | |
730 | * | |
731 | * This is for preparing to put the page under writeout. We leave the page | |
732 | * tagged as dirty in the radix tree so that a concurrent write-for-sync | |
733 | * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage | |
734 | * implementation will run either set_page_writeback() or set_page_dirty(), | |
735 | * at which stage we bring the page's dirty flag and radix-tree dirty tag | |
736 | * back into sync. | |
737 | * | |
738 | * This incoherency between the page's dirty flag and radix-tree tag is | |
739 | * unfortunate, but it only exists while the page is locked. | |
740 | */ | |
741 | int clear_page_dirty_for_io(struct page *page) | |
742 | { | |
743 | struct address_space *mapping = page_mapping(page); | |
744 | ||
745 | if (mapping) { | |
746 | if (TestClearPageDirty(page)) { | |
747 | if (mapping_cap_account_dirty(mapping)) | |
748 | dec_page_state(nr_dirty); | |
749 | return 1; | |
750 | } | |
751 | return 0; | |
752 | } | |
753 | return TestClearPageDirty(page); | |
754 | } | |
755 | EXPORT_SYMBOL(clear_page_dirty_for_io); | |
756 | ||
757 | int test_clear_page_writeback(struct page *page) | |
758 | { | |
759 | struct address_space *mapping = page_mapping(page); | |
760 | int ret; | |
761 | ||
762 | if (mapping) { | |
763 | unsigned long flags; | |
764 | ||
765 | write_lock_irqsave(&mapping->tree_lock, flags); | |
766 | ret = TestClearPageWriteback(page); | |
767 | if (ret) | |
768 | radix_tree_tag_clear(&mapping->page_tree, | |
769 | page_index(page), | |
770 | PAGECACHE_TAG_WRITEBACK); | |
771 | write_unlock_irqrestore(&mapping->tree_lock, flags); | |
772 | } else { | |
773 | ret = TestClearPageWriteback(page); | |
774 | } | |
775 | return ret; | |
776 | } | |
777 | ||
778 | int test_set_page_writeback(struct page *page) | |
779 | { | |
780 | struct address_space *mapping = page_mapping(page); | |
781 | int ret; | |
782 | ||
783 | if (mapping) { | |
784 | unsigned long flags; | |
785 | ||
786 | write_lock_irqsave(&mapping->tree_lock, flags); | |
787 | ret = TestSetPageWriteback(page); | |
788 | if (!ret) | |
789 | radix_tree_tag_set(&mapping->page_tree, | |
790 | page_index(page), | |
791 | PAGECACHE_TAG_WRITEBACK); | |
792 | if (!PageDirty(page)) | |
793 | radix_tree_tag_clear(&mapping->page_tree, | |
794 | page_index(page), | |
795 | PAGECACHE_TAG_DIRTY); | |
796 | write_unlock_irqrestore(&mapping->tree_lock, flags); | |
797 | } else { | |
798 | ret = TestSetPageWriteback(page); | |
799 | } | |
800 | return ret; | |
801 | ||
802 | } | |
803 | EXPORT_SYMBOL(test_set_page_writeback); | |
804 | ||
805 | /* | |
806 | * Return true if any of the pages in the mapping are marged with the | |
807 | * passed tag. | |
808 | */ | |
809 | int mapping_tagged(struct address_space *mapping, int tag) | |
810 | { | |
811 | unsigned long flags; | |
812 | int ret; | |
813 | ||
814 | read_lock_irqsave(&mapping->tree_lock, flags); | |
815 | ret = radix_tree_tagged(&mapping->page_tree, tag); | |
816 | read_unlock_irqrestore(&mapping->tree_lock, flags); | |
817 | return ret; | |
818 | } | |
819 | EXPORT_SYMBOL(mapping_tagged); |